The Audi S4 is the high performance variant of Audi's compact executive car A4. The original Audi S4, built from 1991 until 1994, was a performance-oriented version of Audi's 100saloon/sedan. All subsequent S4s since 1997 have been based on the Audi A4; and as the A4 has evolved from one generation to the next, so has the S4.

A more powerful internal combustion engine, larger upgraded brakes, firmer suspension, larger roadwheels, and distinctive sheetmetal, styling clues and badging have always been amongst the many upgrades the S4 receives over its mainstream 100 and A4 siblings. In markets where the even higher-performance Audi RS4 is not offered, the S4 is the top-of-the-line trim of the A4 family.[1][2]

All versions of the S4 have been manufactured at Audi's plant in Ingolstadt, Germany; they are, or have been available as a four-door five-seat saloon and a five-door five-seat Avant (Audi's name for an estate car/station wagon) body styles since the model's inception in 1991. A two-door four-seat Cabriolet (convertible) S4 variant was introduced as part of the B6 and B7 generation A4 lineups. The B8 Cabriolet has now been built off the A5 coupe body style and the "S" variant is marketed under the Audi S5 nameplate. Although the B8 S4 is rated at only 333hp it can sprint 0-60 in only 4.4 seconds (Motortrend 2014)

Factory production of the original Audi S4 (Typ 4A) began in August 1991 to serve as the performance version of the newly updated C4 platform 100 four-door, five-seat saloon. It was designed to replace the outgoing C3 based Audi 200 quattro turbo, which had been Audi's first true sports-saloon and had been discontinued at the end of 1990.[4][5] Being the first S4 model from Audi, it is commonly referred to as the Ur-S4, derived from the German: Ursprünglich augmentive word (meaning: original).

Audi mildly updated the C4-based model line in 1994 and dropped the 100 nomenclature; all variants of the former Audi 100 line were now re-badged as the Audi A6. In line with the switch in model name, Audi temporarily discontinued the use of the S4 name and began selling an updated but fundamentally identical version of the car, based on the "new" A6 and badged as S6. Despite the change in name, differences between the outgoing S4 and incoming S6 were primarily cosmetic.

A more powerful, more expensive and more exclusive variant known first as the S4 Plus and later as the S6 Plus was available from October 1992 through to July 1994.[3] Built in very small numbers, the "Plus" models featured numerous performance enhancing upgrades; including the use of Audi's 4.2 litre V8 engine in place of the then current inline-five engine.

An all-new C5-based Audi A6 debuted for 1997, after which the S4 and S6 became distinctly separate models based on very different platforms.

The C4 variant S4 ended factory production after less than three years in July 1994.[3]

One of its most renowned owners was Ayrton Senna who owned a silver Avant,[6] not least because he was the Audi distributor for Brazil.

Both five- and six-speed manual transmissions (parts code prefix: 01E, identification codes: five-speed: CBD, CET, six-speed: CBL, CMG) were offered to European customers, but a five-speed manual was the only transmission available in North America; a four-speed automatic transmission (parts code prefix: 01F, identification code: CBF) was available as an option worldwide.[3] Front and rear axle final drive ratio is either 4.111 or 3.889 (dependent on transmission type), and the rear axle (parts code prefix: 017, identification codes: AAT, AET) uses a driver-selectable electro-pneumatic-mechanical switchable diff lock.[3]

Audi's quattro four-wheel-drive system was standard on the C4 S4/S6; a first-generation Torsen-based system which used the "T-1" automatically biasing centre differential (ATB) was used on vehicles equipped with manual transmissions, while a transfer box based system was used on vehicles equipped with an automatic transmission.[3]

S4/S6 "Plus" models equipped with a 4.2 litre 206 kilowatts (280 PS; 276 bhp) all-aluminium alloyV8 engine (parts code prefix: 077, identification code: ABH) became available to European customers as an option from October 1992, only with the six-speed manual gearbox, in either saloon or Avant bodystyles.[3]

All C4 S4s' came equipped as standard with a conventional fixed-assistance rack and pinion power assisted steering (PAS) system. An electronically controlled 'servotronic' system, which varied the level of assistance in accordance with the road speed, was available as an option.[3]

There were two different types of high performance brake systems on offer for the C4 S4.[3] All S4s' initially had 310 millimetres (12.20 in) diameter by 25 millimetres (0.984 in) thick, radially ventilated disc brakes up front, each with an ATE single-piston sliding caliper inside a 'UFO' styled bell-shaped disc. With the introduction of the V8 engine, a new front brake setup became standard; again the discs used radial ventilation, but these front discs were now sized at 314 millimetres (12.36 in) by 30 millimetres (1.181 in) - with a conventionally mounted Lucas-Girling caliper in an external position over the disc. US models had smaller 276 millimetres (10.87 in) discs. The rear brakes, 269 millimetres (10.59 in) by 20 millimetres (0.787 in) and also radially ventilated - remained the same throughout C4 production; they used a Lucas-Girling single-piston sliding caliper with an integrated cable-actuated handbrake mechanism. A Bosch three-channel operation (four-channel sensing) Anti-lock Braking System (ABS) with a mechanical load sensing valve for the rear brakes was standard throughout production.[3]

For roadwheel options, the standard five-arm "Fuchs" forged alloy wheels were 8.0Jx16H2 ET40, and were shod with 225/50 R16 sized tyres. Several other tyre and roadwheel designs were optionally available: a 7.5Jx15H2 ET40 six-spoke with 215/60 R15 tyres, an 8.0Jx16H2 ET40 five-double-spoke, a 7.5Jx16H2 ET35 six spoke "Avus", and an 8.0Jx17H2 ET40 ten-spoke.[3]

The second generation S4 (Typ 8D), now correctly titled Audi S4 quattro debuted in 1997, with factory production commencing October 1997,[3] as part of the facelifted B5 platformAudi A4 line-up, although it wasn't available in North America until late 1999.

In addition to the saloon (sedan), an estate version (wagon)–the Audi S4 Avant–was introduced into the lineup from 1998. Production of the B5 S4 ceased in September 2001,[3] although it was still sold together with the next B6 platform generation through 2002 in North America. Examples produced July 2001 to end of production are 2002 Model Year cars, the 10th digit of the VIN being the number "2".

Several years after it was sold new, the B5 S4 remains a potent enthusiast car, and as featured in the December 2007 issue of Sport Compact Car magazine, a Torque Factory tuned S4 won a comparison test against several other extreme performance cars.[7]

The B5 S4 claims acceleration from 0 to 100 kilometres per hour (0.0 to 62.1 mph) in 5.6 seconds, and had an electronically limited top speed of 250 km/h (155.3 mph), making it both the quickest saloon/sedan in the Audi model line, and among the quickest saloon/sedans in the world at that time.

The Sport Package replaced the wood-grain belt line trim with silver aluminum trim, and the wood grain finish around the shifter with black plastic. The Alcantara seat inserts were silver (on Onyx leather). With the black, white, or blue exteriors, the inserts were also available in blue Alcantara. On the early 2000 models, the Alcantara inserts in the rear seats did not fully extend forward to the front edge of the seat.

The third generation Audi S4 quattro (Typ 8E — saloon: 8E2, Avant: 8E5, and Cabriolet: 8H7) debuted its saloon and Avant bodystyles in Europe in March 2003,[3] and appeared in North America slightly later.[when?] This was based on the latest Volkswagen Group B6 (PL46) platform used by the then current Audi B6 A4. Despite having moved to an entirely new platform, one of the S4's most publicised new features was its new engine - a 4.2 litre V8 engine. Following its initial launch of either a four-door five-seat saloon (sedan), or a five-door five-seat Avant (estate/wagon), it eventually became available in three bodystyles - and for the first time in the Audi 'S' car range, from February 2004, a two-door four-seat Cabriolet (convertible), Typ 8H, was included in the model range.[10]

Official performance figures for standard discipline of sprinting from standstill to 100 kilometres per hour (62.1 mph) in the saloon with manual transmission are 5.6 seconds (Avant 5.8 s, Cabriolet 5.9 s), however, a road test conducted by the American automotive magazine Motor Trend[11] indicated that it could go from a standstill to 60 mph (96.6 km/h) in less than 5 seconds, and make it to 200 km/h (124.3 mph) in slightly over 20 seconds, although doing this led to fuel consumption dipping into single digits. This was considerably worse than the earlier V6 models, leading to the addition of a $1,700 gas guzzler tax (combined 20.2 miles per US gallon (11.6 L/100 km; 24.3 mpg-imp)) for the six-speed manual sedan in the United States. Top speed is electronically limited to 250 km/h (155.3 mph).

The B6 S4 saloon and Avant variants ceased factory production in December 2004, with the Cabriolet ending twelve months later at December 2005.[3]

Discrete lower door trims, along with the now trademark Audi 'S' model vertical-emphasis line grille, and solid aluminium (later replaced with plastic covered by aluminium) exterior door mirrors, and S4 badging front and rear are all that visually distinguish the S4 from its related A4 brethren. In the interior, front and rear Recaroseats (fronts fully electric with the option of heated seats), standard carbon fiber trims, as well as S4 logos in the instrument panel and door sills complete the detail.

The Audi B7 platform Audi S4 quattro, based on the Audi B7 A4, debuted in late 2004. Although Audi classifies it as a new car, the differences between it and the outgoing B6 S4 casually appear to be primarily cosmetic, and is still classified by the internal designation: Typ 8E (although with revised sub-designations - saloon: 8EC, Avant: 8ED, and Cabriolet: 8HE).[3] It has the same 4.2 litre V8 engine (identification code: BBK) as the B6 S4, producing a power output of 253 kilowatts (344 PS; 339 bhp) at 7,000 revolutions per minute (rpm), and 410 newton metres (302 lbf·ft) torque at 3,500 rpm.

There are a few mechanical changes, such as revised springs and dampers and, from model year 2007, an updated Torsen T-3 automatically biasing centre differential, featuring a 'default' asymmetric 40:60 front-rear torque split on manual transmission models, along with the later Bosch ESP 8.0 Electronic Stability Programme[3] and gloss black painted brake calipers.[3] The 'Avus-III' roadwheels now became an option, and were replaced by a standard offering 8.0Jx18 inch 'S-design' 7-spoke forged alloy wheel.[3]

Bose sound system is now standard, whereas it was optional on the B6 S4, and an enhanced optional DVD-ROM-based RNS-E satellite navigation system replaces the previous CD-ROM-based RNS-D option.

In June 2005,[3] Audi announced a limited edition run of 250 special edition S4 saloon cars, celebrating 25 years of quattro four wheel drive. This exclusive model was called the Audi S4 25quattro. Available only in the United States, and only in Avus Silver, the exterior has unique front and rear bumpers, a carbon fibre boot lip spoiler and lower front splitter. 15-spoke DTM alloy wheels, along with optional dealer-fitted 'Audi four-rings' decals for the front doors complete the exterior makeover. Black and grey contrasting interior leathers, along with "quattro" embossed into the Recaro seats, together with an individually numbered exclusive quattro gear shift knob for the manual-only gearbox define the interior changes.

On the mechanical side, the S4 25quattro was the second Audi, after the B7 RS4 to be fitted with the latest Torsen T-3 asymmetric ATB centre differential for its quattro permanent four-wheel drive system. Under normal grip conditions, this is set with a default rearwards torque distribution bias of 40:60 front to rear, and a maximum of 100% torque can automatically be apportioned to the rear axle (and up to 80% to the front) as conditions warrant. The final drive ratios are 3.889.

From November 2008, the latest generation of the 'Audi S4 quattro'[12] (Typ 8K) entered factory production.[3] It is based on the current Audi B8 A4,[13] built on the Volkswagen Group MLB/MLP platform. Unlike the previous B6 and B7 models, the new B8 version will only be available as a four-door five-seat saloon (sedan), or a five-door five-seat Avant (estate/wagon). The sport-performance two-door four-seat Cabriolet (convertible) mantle is now taken by the current Audi S5 Cabriolet and new Coupe. Unlike previous generations of the S4, only the sedan will be imported to the United States and Canada.

The previous B6/B7 S4s were the top-of-the-line models in North America, ahead of the 3.2L V6 and 4-cylinder 2.0T A4s, and competed with the BMW M3 which at the time had a high-rev 3.2 L inline 6. The 3.0 TFSI V6 engine replaces the 3.2 litre FSI V6 as the upgrade engine in the A4 and A6 lineups starting for 2009; both the 3.2 litre FSI and 3.0 TFSI were offered together until the end of the 2010 model year.[14] The 3.2L V6 engine is no longer offered in the A4 lineup from the 2011 model year onwards, so the recently introduced B8 S4 is now priced 9% lower than its V8 predecessors, and slots directly above the 4-cylinder 2.0T base model. The S4 now compares more closely with the BMW 335i.

Previously unavailable enthusiast driver aids are now optional, such as Audi's Sport Rear Differential, active steering and adaptive damping suspension (part of the Audi Drive Select Package). The front axle was moved by 6.1 inches to the front, which improved the weight distribution of the B8 Platform. Combined with the Sport Rear Differential Audi was able to greatly improve the weight balance and dynamics of the S4 over previous models.[15][16][17]

A new designed roadwheel is included on the B8 S4, an 8.5Jx18" '5-double-spoke S' design alloy wheel with 245/40 ZR18 high performance tyres. Optional 19 inch wheel and tyre packages are also available, sized at 8.5Jx19" alloy wheels with 255/35 ZR19 tyres. LED tail lights are standard fitment, along with Audi's now-trademark LED daytime running lights at the front.

This engine is mated to either a six-speed manual transmission (identification code: KMR)[3] or a seven-speed 'S tronic' DL501[20]dual clutch transmission[21] (identification code: LHK),[3] the latter with steering wheel mounted paddle-shifters for tiptronic gear selection, which replaces the Tiptronic automatic transmissions found in the B6/B7 iterations. The 'Audi quattro Sports differential' fitted in the rear axle final drive unit is available as an option.

Acceleration from standstill to 100 kilometres per hour (62.1 mph) takes 5.1 seconds[22] for the saloon with manual gearbox, the Avant one tenth of a second slower at 5.2 seconds. The same dash to 100 km/h in the saloon with S tronic takes 5.3 seconds, and the Avant at 5.4 seconds. The top speed is electronically limited to 250 kilometres per hour (155.3 mph). However a comparison in the American automotive magazine "Road & Track"[23] showed the sprint from 0 to 60 mph in only 4.5 seconds for the 6-speed manual transmission. With figures like these, the B8 S4 accelerates more quickly than its V8-engined predecessors.[1] Audi of America claims that the version of the S4 achieves 28 highway miles per gallon, and a 0 to 60 miles per hour (96.6 km/h) acceleration time of 4.9 seconds with the manual transmission[24] and 5.1 seconds with the S tronic.[25] Fuel consumption is rated at a combined 24.2 miles per US gallon (9.7 L/100 km; 29.1 mpg-imp).[22] Therefore, the B8 S4, unlike the V8-powered B6/7 models, avoids the US gas guzzler tax. The B8 S4's 3.0 TFSI engine also gets only 1 m.p.g. less than the base 2.0 TFSI engine.[26] This is one of the most important reasons for Audi to downsize their engines, while keeping the output equivalent better, by using forced-induction such as supercharging or turbocharging.[1]

The same engine is shared with the Audi S5 Cabriolet (though the 7-speed S Tronic is the sole transmission) and the 2013 Audi S5 Coupe. Detuned versions of this engine making 310 hp (231 kW) are found in the 2009-11 Audi A6 3.0 TFSI (C6) mated to a 6-speed TipTronic automatic transmission, the 2012 Audi A6 3.0 TFSI (C7) and 2012 Audi A7 3.0 TFSI, the latter two which are paired with an 8-speed TipTronic automatic.